Hemlines change, ateliers crumble and designers get disgraced, but there is, it seems, one fashion constant: the industry's capacity for gross cultural insensitivity.

Joining a pantheon whose recent inductees include those lovely Vogue Italia "slave" earrings, is a new faux pas that will be remembered by the three words "Navajo Hipster Panty". (If ever there were a phrase to make Ke$ha, with her tribal face paint, blush with shame this, surely, must be it.)

This week, in an open letter to Urban Outfitters that's as funny as it is trenchant, a Native American woman called Sasha Houston Brown takes the company's CEO to task for their "Navajo" range.

She decries the store's "plastic dreamcatchers wrapped in pleather", and fulminates over their "indistinguishable mass of artificial feather jewelry and hyper sexualized clothing featuring an abundance of suede, fringe and inauthentic tribal patterns." They amount, she says, "to a mass marketed [sic] collection of distasteful and racially demeaning apparel and décor" adding, "I take personal offense to the blatant racism and perverted cultural appropriation your store features this season as "fashion.""

The company's 21-strong range of Navajo branded items includes clothing, bracelets, plimsoles and a hipflask but the most egregious item has to be those pants. Eight dollars will buy you a cotton and spandex blend in orange diamond print which, as one happy online customer attests, "make my bum look delicious."

But this isn't just a question of taste or lack of; it's also a potential legal issue. By using the term 'Navajo' Urban Outfitters could be breaching the The Federal Indian Arts And Crafts Act which dates from 1990. It made it illegal "to offer or display for sale, or sell any art or craft product in a manner that falsely suggests it is Indian produced, an Indian product, or the product of a particular Indian or Indian Tribe or Indian arts and crafts organization."

Urban Outfitters's PR Director, Ed Looram, told the website Jezebel that: "The Native American-inspired trend and specifically the term 'Navajo' have been cycling thru [sic] fashion, fine art and design for the last few years. We currently have no plans to modify or discontinue any of these products."

But the ubiquity of 'Navajo' as a fashion term doesn't legitimise it. Unlike 'bodycon' or 'glunge' (sorry), this isn't something cooked up by a fashion editor. The word refers to a semi-autonomous, Native-American governed area of land home to around 300, 000 Navajo people. Their judiciary - the Navajo Nation Department of Justice - have sent a cease and desist letter to Urban Outfitters. As Jezebel reports, Brian Lewis, an attorney for the Navajo Nation, has said: "the Nation is cautiously optimistic that it can discuss this issue with the Urban Outfitters Corporation and convince it to adopt another name and trademark for its products."

Urban Outfitters are by no means the only ones guilty of appropriating Native American dress. On her blog Native Appropriations, Cherokee grad student Adrienne K argues that wearing those feathered headresses, so beloved of Ke$ha and annoying girls at festivals everywhere, is "just as bad as running around in a pope hat and a bikini, or a Sikh turban cause it's 'cute'."

The trend for "super cute Native American clothes" is lampooned in this very funny video, complete with closing dig at Urban Outfitters ("Urban Infitters"). Be warned though, it includes the line, "to me, genocide means out with the old and in with the new." Since fashion seems as happy to appropriate parody as it does oppressed cultures (compare the Derelicte line from Zoolander to Vogue India's 'third world chic' shoot) let's just hope no designer sees those 'Concentration Couture' striped pyjamas.